I have a new Big Country with two 6v batteries. They were fully charged when the unit went into storage about a month ago. It will be in storage for another 5 months or so before we use it. We are in a cold climate area with temeratures well below the freezing mark for long periods and there will be several very cold periods of -20 to -30 and possibly colder. I used to leave my batteries in our RV's when it was parked near the house and I could plug it in a few times over the winter, however we have moved and don't have room now to park it in the yard. Any advice is appreciated.